20721156 has 24 divisors (see below), whose sum is σ = 48563424. Its totient is φ = 6876480.

The previous prime is 20721143. The next prime is 20721161. The reversal of 20721156 is 65112702.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 910 + ... + 6501.

It is an arithmetic number, because the mean of its divisors is an integer number (2023476).

Almost surely, 2^20721156 is an apocalyptic number.

It is an amenable number.

20721156 is an abundant number, since it is smaller than the sum of its proper divisors (27842268).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20721156 is a wasteful number, since it uses less digits than its factorization.

20721156 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7651 (or 7649 counting only the distinct ones).

The product of its (nonzero) digits is 840, while the sum is 24.

The square root of 20721156 is about 4552.0496482354. The cubic root of 20721156 is about 274.6658464749.

Adding to 20721156 its reverse (65112702), we get a palindrome (85833858).

The spelling of 20721156 in words is "twenty million, seven hundred twenty-one thousand, one hundred fifty-six".